The present invention relates to vehicle structures made of steel structural components or elements, one or more of which is made by a process known as hydroforming. Hydroforming per se is known and involves placing a tube or some other hollow element into an appropriate mold or tool, locking off the ends of the tube or other hollow element, and then forcing a liquid, such as water, at a high pressure into the interior of the tube. Pressures which are quite high are necessary to produce hydroformed elements having sharp bends or steps incorporated in them.
The result of the hydroforming process is essentially to deform or "blow up" the tube so that it conforms to the inner surface of the mold or tool. Some limitations on the use of hydroforming are present, since the material forming the tube can be stretched or deformed only to a certain degree. Also, the hydroforming process is quite time consuming as compared to conventional stamping or similar deformation processes. However, assuming that a tube to be hydroformed has an approximately constant thickness, it will be stretched or deformed evenly over its surface area. Hydroformed elements, therefore, have certain advantageous strength characteristics.